The present FIG. 1 is a schematic diagram of a composition framework of EPS (Evolved Packet System) of 3GPP (3rd Generation Partnership Project). As shown in FIG. 1, the EPS network framework in a non-roaming scenario includes: E-UTRAN (Evolved Universal Terrestrial Radio Access Network), MME (Mobility Management Entity), S-GW (Serving Gateway), PDN GW (also called as P-GW, Packet Data Network Gateway), HSS (Home Subscriber Server), PCRF (Policy and Charging Rules Function) entities and other supporting nodes.
Wherein, the PCRF is a core of the PCC (Policy and Charging Control), and is responsible for formulating policy strategy and charging rules. The PCRF provides network controlling rules based on service data stream, and the network controlling includes service data stream detection, gating control, QoS (Quality of Service) control and charging rules based on data stream and so on. The PCRF sends the policy and charging rules formulated by itself to the PCEF (Policy and Charging Enforcement Function) for enforcement. Meanwhile, the PCRF is also required to ensure that the rules are coincident with the subscribers' subscription information. The basis for the PCRF to formulate policy and charging rules includes: acquiring service-related information from AF (Application Function); acquiring subscribers' subscription information of policy and charging control from SPR (Subscription Profile Repository); and acquiring bearer-related network information from PCEF.
The EPS supports communication with non-3GPP systems, and the EPS communicates with non-3GPP systems through S2a/b/c interfaces, using a P-GW as an anchor between 3GPP systems and non-3GPP systems. As shown in FIG. 1, non-3GPP systems are classified into trusted non-3GPP IP access and untrusted non-3GPP IP access. The trusted non-3GPP IP access can be connected with a P-GW through an S2a interface directly; the untrusted non-3GPP IP access is required to connect with P-GW through ePDG (Evolved Packet Data Gateway), where an interface between an ePDG and a P-GW is an S2B interface, and signaling and data between UE (User Equipment) and ePDG are encrypted for protection with IPSec (Internet Protocol Security). The S2c interface provides control and mobility support related to the user side between UE and P-GW, and the mobility management protocol supported by the S2c interface is DSMIPv6 (Mobile IPv6 Support for Dual Stack Hosts and Routers).
With the development of network technology, many operators begin to concern FMC (Fixed Mobile Convergence), and research on the connection and communication between 3GPP and BBF. In the scenario that subscribers access the mobile core network through BBF, it needs to ensure the QoS of the data in the whole transmission path (data may be transmitted through fixed network and mobile network). In the related art, the QoS is ensured by interacting with BPCF (Broadband Policy Control Framework) in the BBF access through PCRF. BPCF is the policy control framework of BBF access. For the resource request message of PCRF, BPCF performs, according to the network policy, subscription information and so on of the BBF access, resource admission control or forwards the resource request message to other network elements of the BBF access network (such as BNG (Broadband Network Gateway)), and then other network elements perform the resource admission control (i.e. other network elements are entrusted to perform resource admission control). For example, when a UE accesses the 3GPP core network through WLAN (Wireless Local Area Network), PCRF needs to interact with BPCF when performing QoS authorization in order to ensure a demand for a total bandwidth for visiting services by all the UEs accessing through WLAN accessing line being not larger than the bandwidth of the line (such as the subscription bandwidth or the largest physical agent supported by the line), thus the BBF access network performs resource admission control.
At present, one important scenario of studying interconnection and intercommunication between 3GPP and BBF is: a scenario of a 3GPP UE accessing the EPS through the WLAN of BBF. Many operators think that WLAN can be taken as a trusted non-3GPP system, thereby the problem of interconnection and intercommunication for UE accessing EPS through the trusted WLAN has been attached importance gradually and on the start of research. FIG. 2 is a schematic diagram of the framework for a UE accessing an EPC (Evolved Packet Core) network through WLAN in the related art, wherein, one logic network element of the WLAN interconnects with P-GW of 3GPP through an S2a interface, and the S2a interface supports GTP (Generic Tunneling Protocol)/PMIP (Proxy Mobile IP).
In the related art, to make AC (Access Controller)/BNG (Broadband Network Gateway) support S2a interface, all AC/BNG devices are required to upgrade, which will seriously impacts the present network.
In order to solve the problem, in the related art, it proposes to introduce a WLAN access network (such as TWAG′ (Trusted WLAN Access Gateway) as shown in FIG. 3), by this way, accessing the 3GPP network can be implemented without need of upgrading the AC/BNG devices on a large scale, as a result, upgrading and modification for the present network are lessened. In that framework, TWAG′ is added to WLAN, which is responsible for the intercommunication of the control plane messages and user plane data between WLAN and EPC network. Wherein, TWAG′ can be deployed alone, and can also be integrated in BSG (Broadband Service Gateway). In that framework, the related critical interfaces and functions thereof are described as follows:
Interface C: is an interface between TWAG′ and BBF AAA (Authentication, Authorization and Accounting). That interface is used to forward the authentication message sent by BNG or BBF AAA, and the authentication success message sent by BBF AAA can be used to trigger the establishment of GTP/PMIP tunnel between TWAG′ and P-GW of the EPC network.
Interface D: is an interface between TWAG′ and BNG. That interface is used to forward authentication message sent by BNG or DHCP (Dynamic Host Configuration Protocol) message, and subscriber data etc.
However, there is still no solution of implementing policy control in the network framework as shown in FIG. 3.